Coming from a Roland interface I think that QuadCapture may be part of your poor situation ... I could never obtain full stability while I was still on the Roland audio drivers. While it got somewhat better with Platinum, it only got resolved properly when switching to a different interface brand.
 
Also, X3 is old. Melodyne 4 is new. I even had issues (minor ones, no crashes though) with Platinum and Melodyne 2.x which were much closer in sync ... problems disappeared once I upgraded to Melodyne 4 which seems to go fine with Platinum.

one more vote for Splat.
It´s working flawless in my box except a phase from early Nov -
end dec 16.
I recommend to try the SPLAT demo.
 

One more vote to try Splat demo.  I have not had any problems with Splat and Melodyne editor 4.  I am running the latest release -2017.01 - and on Windows 10.

The only issue I've had with Melodyne is if I have too many unrendered clips, so I got into rendering after tweaking.
 
The Roland drivers could also be an issue. I had lots of problems with the Octa-Capture and Windows 7. Those problems went away when I updated to Windows 10 and got Splatified. I do think the Windows 10/Splat combo is optimum. 
 
As to the Mac, yes it works but there are no guarantees. A person I collaborate with musically got fed up with the Mac and two DAWs he ran on it (he ran two because one crashed all the time), took the leap to Windows and SONAR, and never looked back.
 
 
 
 

You're experiencing crashes and reliability issues with your Sonar install. So you're comparing your Sonar experience to your recent experience using some other software on a Mac and based on that, you're considering making the jump to Mac, the perception being the Mac is a more reliable platform.
 
That's fine, but you might want to look hard at your study design before you go making any conclusions based on results.
 
How old DAW software you're running at home. How old are the plugs you're running at home. When was the last time you did a complete hard drive wipe/clean install of your software?
 
 
How old is the DAW software running on the Mac? How old are the plugs running on Mac? When was the last time that Mac saw a complete hard drive wipe/clean install of its software?
 
When the answers to all those questions match exactly, then and only then will you be able to determine if the Mac is the better platform for what you're trying to do.
 
 

I don't know your budget or the upgrade cost, but a onetime purchase to the lifetime Platinum seemed like a no-brainer to me. It's always there for projects if I need it at no further cost, no matter what else I use.

There is always two sides to the story. I recently got an iMac and have been setting it up with audio software. Currently I am running the Windows version of Studio One but installed the Mac version and I must say it is all working pretty well. It works flawlessly with Melodyne on the Win setup and the same on the Mac machine.
 
It also sounds like it can run well with Sonar too so maybe look into trouble shooting a bit perhaps. Melodyne should basically never crash and simply be pulled in when needed and put back in the background when not. I also like to render parts once I am happy with them after Melodyne has been applied. keeping the original files of course.

I like Cakewalk and have no plans to change; but *IF* I changed, it would be to Logic Pro on Mac.

eph221
There's not a day goes by that something goofy doesn't happen with SPLAT.  Seriously.  

Why is that the case?

FWIW - A friend of mine got tired of the problems he was having with Windows, virus protection and such so he sold everything and bought a Mac.  He was bragging to everyone about the ease of using it and the fact that it was so safe to use on-line.  About 8 months later he was crying the blues.  He got a virus and loss all of his programs and data. He didn't think that he needed any backups with a Mac.
 
Moral of the story is the old "the grass looks greener on the other side" ain't necessarily true.